1. Field of the Invention
This invention relates generally to the field of computer graphics, and more particularly, without limitation to entering of information presentations.
2. Prior Art
Graphics are the easiest way to communicate information. The creation of graphic layouts or charts has progressed from manual pen and paper generation techniques to computer-aided techniques. Previously developed computer graphics programs or applications generally provide clean, professional graphics in a fraction of the time required for handwritten graphics.
However, these computer programs can be complicated to use and require many user interactions in order to enter an information presentation with logically arranged graphical objects. This is especially true for information presentations, i.e. for material that is intended to be viewed and manipulated by people, such as graphical user interfaces, World Wide Web documents, and conventional newspapers and magazines.
A presentation's layout can have a significant impact on how well it communicates information to and obtains information from those who interact with it. For example, the importance of individual objects can be emphasised or de-emphasised, and the relationships between objects can be made more or less clear. A well laid out presentation can visually guide a viewer to infer correct relationships about its objects, and to accomplish tasks quickly and correctly, e.g. by minimising the distance between objects to be manipulated sequentially, increasing the presentation's effectiveness.
The vast majority of layouts, even if made using a computer, are being created without much automatic support: A human graphic designer or “layout expert” makes most, if not all, of the decisions about the position and size of graphical objects to be used.
A simple approach to simplify the task of creating layouts, which is widely available in computer graphics programs, is to align graphical elements with an equally-spaced rectangular grid. A problem with this approach is that, in order to benefit from this grid, an object must span an integral number of fields in width and height. For example, two graphical objects, one spanning an even number of fields and the other an odd number, cannot be centered with respect to each other and both still lie on the grid.
To overcome this problem, graphics programs usually also allow the alignment of objects in relation to each other. This alignment is applied once when the user issues the appropriate demand, but is not maintained during later editing.
The vast majority of research in automated layout is focused on constraint-based methods. Spatial constraints define a certain alignment or size relationship between objects. Once they have been imposed on graphical objects, a constraint solver maintains them permanently across other editing operations. Constraints can also impose higher-level requirements, such as text formatting and sizing guidelines or object-type-dependent size and alignment constraints. Constraints are very powerful tools for layout generation. The main challenge, and a limitation to application in commercial products today, is to create a suitable user interface for intuitively specifying the abstract mathematical descriptions suitable for automatic constraint solving.
An overview of the prior art in constraint-based methods and constraint solvers, is provided in “A survey of automated layout techniques for information presentations”, Simon Lok and Steven Feiner, Smart Graphics 2001, Hawthorne, N.Y., USA, the entirety of which is herein incorporated by reference.